Process for the oxidation of nitrogen in electric furnaces



. 1 o. JENSEN PROCESS FOR THE OXIDATION OF NITROGEN IN ELECTRIC FURNACES Filed Jan. 10, 1922 v [SDI/er V Hsa/ Excbanygr wwwetented line. as, race.

SAES

-aranr OLAF JENSEN, OF NOTODDEN, NGRWAY, KVAELSLQFAKTIESELSKAB,

ASSIG-NDR TO NORSK HYDRO-ELEKTRISK OF CHRISTIANIA, NORWAY.

application filled January 10, 1922. Serial No. 528,233.

To all whom it may concern:

Be it known that I, OLAF JnNsnN, chemical engineer, a citizen of the Kingdom of Norway, residing at Notodden, Norway,

have invented certain new and use Improvements in Processes for the Oxidation of Nitrogen in Electric Furnaces, of which the following is a smcification It has been known for some time that the yield of combined nitrogen per kw. in the electric arc furnaces can be, increased by.

adding oxygen to the air employed. It operation with such addition of oxygen is to prove renumerative the gases must be returned from the absorption system to the electric furnaces.

Experience has be done directly if the nitrous gases are absorbed in aqueous solutions or in water.

Gases coming from such an absorption system are saturated with moisture and this diminishes the output. Careful experiments have proved that the output depends on the moisture of the gases, in that the output diminishes as the moisture of the gases increases. NVhere circulation is employed the pipes and machinery will also be exposed to the destructive eiiect of the moist gases, which always contain a certain quantity of 80 nitrogenous oxide. v This can, of course, be avoided by drying the gases with sulphuric acid. Since, however, large quantities of gas have to be dried, about 20000 cubic meters per hour for 10000 as kw., a large amount of concentrated sulphuric acid is required, and this will have to be reconcentrated.

The present invention provides a process by which it is possible to dry the circulating 40 gases to such an extent that the yield is not diminished, while, at the same time, corrosion of the pipes and compressors by the moisture is prevented. The process consists in conducting the ases from the absorption towers into a rerigerating apparatus, for instance, a tower over which co d liquid is continually flowing. The gas is cooled in this tower to, for instance, 10 while atthe same time the so moisture diminishes until the vapour pressure'of the gas and of the liquid isequal.

If cold water is used the gas will be setproved that this cannot V urated with moisture at 10. If, on the other hand, a cool solution of nitrate of lime is used, the gas will contain less 56 moisture. As the gas which comes out of the refrigeration plant contains nitrous gases, it will, saturated with moisture, have a strongly corrosive sheet on the iron pipes and the compressors which imel the gas so into the electric furnaces. iiv is prevented in accordance with the present inventron by heating the gas to, for instance, -70.. The relative humidity of the gas will then be so small that there will not be as any condensation on the pipes or the ma= chinery.

One manner of carrying out the invention practically is illustrated diagrammatically in the accompanying drawing.

After the gases, from the electric furnace have passed an ordinary system consisting of. steam boiler, refrigeration plant, oxida- 'tidn tank and absorption towers, they are conducted into a refrigeration tower over it which cold water at 10 continually flows. The cool gases then as through a. heat exchanger after first liaving passed through a suitable mist filter not shown in the drawmg. The gases are heated in the heat cxno changer to 600. They are conducted from the heat exchanger-birch to the electric furnace by means of a suitable pump. In this way a safe apparatus is obtained. The supplementary gas which is added to keep the composition of the gas constant is added to the gas before it reaches the pump.

1 claim:

1. Process for the oxidation of nitrogen in electric furnaces and obtaining nitrogen products which comprises circulating the gas through a system including an absorption tower, bringing the gases from the absorp tion tower into direct Contact with a cooling liquid and then heating said gases to so hi h a temperature that no condensation will ta e. place in the pipes or machinery. I

*2. In the cyclic process of ox ing'nitrogen in electric furnaces the steps which consist in absorbing the gaseous reaction products in an aqueous medium, cooling the absorbed gases, and thereafter elevating-the temperature of the gases to such degree that condensation isavoided.

3. In the cyclic process of oxidizing nitrogen in elecsric furnaces; the steps which consist in absorbing the gaseous reaction producis in an aqueous medium, cooling the absorbed gases by direct contactwith liquid cooling means, thei'eafcer elevating the temn-erature of the gases to such degree that condensation is avoided, and adding oxygen to the cycle before return df the gases to the furnace and after elevation of the temperature.

In testimony whereof, I af'fix my signs-.-

ture. 1

OLAF ENSEN. 

